1. Field of the Invention
The present invention relates generally to disc cartridges and, more particularly, is directed to a disc cartridge for keeping therein a disc-shaped recording medium in such a fashion that the disc-shaped recording medium can be recorded and/or reproduced in that state.
2. Description of the Prior Art
A known disc cartridge is so arranged as to keep therein a disc-shaped recording medium such as a so-called compact disc or the like in such a fashion that the disc-shaped recording medium can be reproduced in that state. Conventionally, this type of a disc cartridge is provided with a lid hinged to a housing main body to be freely openable and closable to exchange a disc-shaped recording medium.
When the disc cartridge is arranged to be freely openable and closable as described above, the disc cartridge must be provided with a lock device to prevent the lid from being opened inadvertently under the condition that the disc-shaped recording medium is kept in the disc cartridge with its lid closed. In practice, it is desired that such lock device is easy to handle to release the lid from locking.
To this end, such a lock device is proposed and is disclosed in Japanese Utility Model Laid-Open Gazette No. 61-52377. An example of such a conventional lock device will be described hereinafter with reference to FIGS. 1 to 3.
Referring to FIG. 1, there is shown a disc cartridge 1 which generally comprises a housing main body 2 and a lid 3, which is made of a transparent synthetic resin material and is hinged to the housing main body 2 to be freely openable and closable. A cut-away concave portion 4 which takes the form of concavity is formed near each of both sides of the front end portion of a main wall portion 2a of the housing main body 2, and a lock release operation portion 5 is located within each of the cut-away concaved portions 4.
The lock release operation portion 5 will be described more fully. That is, as shown in FIG. 2, on the bottom surface of the cut-away concaved portion 4, there are formed two arm members 5a and 5b side-by-side with a predetermined spacing in the left and right directions. The two arm members 5a and 5b can respectively be extended forward and elastically deformed. As illustrated in FIG. 2, to the front end portions of the arm members 5a and 5b, there is fixed a release operation button 5c so as to extend across both the arm members 5a and 5b. On the upper portion of the front end of the arm member 5a, there is formed a lock nail member 5d which is protruded in the lateral direction. When the lid 3 is closed, as shown in FIG. 3A, this lock nail member 5d is engaged with a hook portion 6 formed on the lower surface of the front end portion of the lid 3, thus the lid 3 being locked.
In the thus constructed lock release operation portion 5, when the user touches the front surface of the lock release operation button 5c with his fingers and operates the same, both the arm members 5a and 5b are elastically deformed so that the release operation button 5c and the arm members 5a and 5b are displaced in the row direction in which the arm members 5a and 5b are provided side by side that is, in the direction shown by an arrow A in FIG. 3A. Accordingly, when the release operation button 5c is moved in the direction shown by an arrow A1 in FIG. 3B, as shown in this figure, the lock nail member 5d formed on the arm member 5a is disengaged from the hook portion 6 of the lid 3 to thereby break the locking of the lid 3, thus the lid 3 being opened to, for example, exchange a disc-shaped recording medium D (hereinafter simply referred to as a disc D).
As described above, according to the lock device used in the conventional disc cartridge, the lid 3 is locked to and released from the housing main body 2 by elastically deforming the two arm members 5a and 5b.
Referring back to FIG. 1, a concaved portion 2b is formed on the main wall portion 2a of the housing main body 2, and the shape of this concaved portion 2b is selected to be substantially the same as the outer peripheral shape of the disc D to keep the disc D in the concaved portion 2b. When kept in the disc cartridge 1, the disc D is restricted from moving within the housing main body 2 by the concaved portion 2b, and this concaved portion 2b can protect the outer peripheral edge of the disc D and also the recording portion of the disc D.
Further, through the concaved portion 2b of the housing main body 2, there are formed an insertion opening 2c into which a disc table of a recording and/or reproducing apparatus (not shown) is inserted when the disc cartridge 1 is loaded to the main body of the recording and/or reproducing apparatus and an opening 2d through which the disc D is exposed in part to the outside to enable a pickup device of the recording and/or reproducing apparatus to record on and/or reproduce from the disc D an information. The disc table (not shown) inserted through the insertion opening 2c holds the disc D with the aid of a support member 3a formed rotatably on the rear surface of the lid 3 and rotates the disc D in such a fashion that the disc D is floated above the bottom surface of the concaved portion 2b of the housing main body 2 by a predetermined amount.
In order to prevent dusts, smudges or the like from adhering through the opening portion 2d of the housing main body 2 to the disc D kept in the disc cartridge 1 upon non-use and also to protect the disc D from fingermarks when the disc cartridge 1 is loaded onto or ejected from the recording and/or reproducing apparatus, a shutter S is mounted on the housing main body 2 to become freely rotatable in the directions shown by arrows P1 and P2 in FIG. 1. The shutter S is provided with a slit S1 having a width equal to or wider than that of the opening portion 2d of the housing main body 2. When the shutter S is rotated in the direction shown by the arrow P2, the opening portion 2d is opened to enable the pickup device to read and/or record the information from and/or on the disc D. When the shutter S is rotated in the direction shown by the arrow P1, the opening portion 2d is closed to protect the disc D from the dusts, smudges, fingermarks, etc.
In this prior art example, the lock release operation portion 5 is formed as a quadrilateral by connecting the front ends of the two arm members 5a and 5b extended forward from the bottom surface of the cut-away concaved portion 4 with a predetermined spacing by the release operation button 5c so that when two arm members 5a and 5b are elastically deformed by operating the release operation button 5c, two arm members 5a and 5b interfere with each other to thereby reduce their freedom in being elastically deformed. As a result, the engaging amount of the lock nail member 5d formed on one arm member 5a with the hook portion 6 formed on the rear surface of the lid 3 must be reduced. Further, since the lock release operation button 5c is served as the free end portion, the lock release operation button 5c is twisted easily with the result that the engaging amount of the lock nail member 5d with the hook portion 6 becomes further smaller. This makes the locking imperfect, and there is a risk that the lock nail member 5d will be disengaged from the hook portion 6 inadvertently. In addition, since the two arm members 5a and 5b interfere with each other, they are made easy to break by the accumulated stress. Thus, the life span thereof will be shortened.
The pickup device to read and/or record a signal from and/or on the disc-shaped recording medium D is generally arranged such that its objective lens is placed at substantially the central position in the left to right direction of the opening portion 2d and then moved along the radius direction of the disc D. However, since the pickup device is so arranged as to incorporate in its housing an objective-lens-drive mechanism to adjust the objective lens in the focussing and tracking directions, the pickup device will be offset in either of right and left directions of the center line along the radius direction of the disc D through the opening portion 2d of the disc cartridge main body 2. Accordingly, if the opening portion 2d is formed through the disc cartridge main body 2 so as to correspond to the pickup device offset in either of the right and left directions, this disc cartridge can not be recorded and/or reproduced by a recording and/or reproducing apparatus having other type of a pickup device. That is, the disc cartridge disclosed in Japanese Utility Model Laid-Open Gazette No. 61-52377 can not be applied to various types of pickup devices. Therefore, it may be considered that only the objective lens of the pickup device be inserted into the opening portion 2d of the disc cartridge main body 2. In that case, since the distance between the disc surface of the disc D and the surface of the objective lens is so small that by the up and down movements of the disc D, the disc surface of the disc D and the surface of the objective lens contact with each other. There is then a possibility that the surface of the disc D and the surface of the objective lens will be scratched and then damaged.